1. Field of the Invention
The present invention relates to drug coatings that can be formed within or over dosage forms to deliver one or more insoluble or soluble drugs. In particular, the present invention provides drug coatings, coating formulations and methods that provide aqueous-based drug coatings that exhibit high loading of at least one insoluble drug, can be loaded with one or more insoluble drugs in combination with one or more insoluble drugs, and may be applied to a variety of different dosage forms.
2. State of the Art
Drug coatings are known in the art. For example, U.S. Pat. Nos. 4,576,604, 4,717,569, 4,763,405, 5,273,760, 5,286,493, 5,407,686, 5,998,478, 6,004,582 and 6,136,345, the contents of each of which are incorporated herein in their entirety by reference, teach various different drug coating formulations designed to provide the immediate release of one or more drugs of interest. In addition, International Applications numbered WO 96/10996, WO 99/55313, WO 00/35426 and WO 01/51038, the contents of which are incorporated herein in their entirety by reference, also teach various different drug coating formulations that may be provided over various different dosage forms. Drug coatings that can be coated over dosage forms are useful for a variety of reasons. In particular, the use of a drug-containing overcoat can impart multiple performance characteristics to a single dosage form. For example, a dosage form providing the controlled release of one or more drugs can be coated with an immediate release drug overcoat to provide a dosage form that combines the benefits of an immediate release dosage form with the benefits of a controlled release dosage form.
Where a coating formulation is to be used to provide a drug coating over or within a dosage form, the coating formulation should provide drug loading characteristics that permit therapeutic dosing of the drug incorporated in the coating, while maintaining desirable coating characteristics. The loading characteristics of a drug coating become especially important as the desired dose of drug to be delivered from the drug coating increases. As the required dose increases, the drug loading performance of the drug coating formulation must also increase. If the drug coating formulation does not exhibit sufficient drug loading, the thickness of a coating required to deliver a desired dose of drug may increase to such an extent that manufacturing, cosmetic, and patient compliance issues may be encountered.
Moreover, although, drug coatings can be prepared from organic solvents or solvent systems containing one or more organic solvents, the use of organic solvents presents several potential disadvantages. Organic solvents are relatively costly, often volatile, are potentially harmful to the environment, and create potential health hazards for workers. Because of the potential harm organic solvents present to workers and the environment, the use of organic solvents in a manufacturing process typically creates various regulatory hurdles that must be overcome. Moreover, where organic solvents are used to produce drug coatings, some residual amount of solvent may remain in the finished coating, which, depending on the amount and the solvent used, may be harmful to an intended subject. In light of the potential disadvantages presented by organic solvents, it is generally preferred to formulate drug coatings and coating compositions using solvents or solvent systems that do not include organic solvents
In particular, where possible, it is typically preferable to formulate drug coatings using an aqueous solvent, such as purified water. It would be desirable, therefore, to provide a drug coating that not only can be coated from an aqueous coating composition, but also exhibits drug loading capabilities that facilitate delivery of a wide range of drug doses from coatings having physical and aesthetic characteristics suitable for commercial production. Ideally, such a drug coatings could be formulated to include high concentrations of even water insoluble drugs, or combinations of one or more water insoluble drugs with one or more water soluble drugs.